WASHINGTON — President Donald Trump and House leaders are revving up pressure on balky conservatives and other Republican lawmakers as crunch time approaches on the party’s health care overhaul bill, a drive GOP leaders concede they can’t afford to lose.

A day before the House planned votes on the measure, Trump was expected to continue hunting support for what would be a significant achievement for his young presidency. But underscoring the bill’s uncertain fate, a senior administration official said that 20 to 25 House Republicans remained opposed or undecided. That’s a grave figure since united Democratic opposition means the measure crashes if 22 GOP lawmakers vote “no.”

“If we keep our promise, people will reward us,” House Speaker Paul Ryan, R-Wis., told reporters Tuesday of GOP vows to demolish former President Barack Obama’s health care law that the GOP has assailed since its enactment in 2010. “If we don’t keep our promise, it will be very hard to manage this,” the speaker said.

“Honestly, a loss is not acceptable, folks,” Trump told lawmakers at a closed-door Capitol meeting with House Republicans. He warned they’d face widespread defeats in next year’s elections and possible loss of control of the chamber if the measure failed.

Trump’s remarks and the White House nose count of votes were each described by Republicans who provided inside information on condition of anonymity.

Emerging from the meeting at the Capitol, Rep. Chris Collins, R-N.Y., said Trump told Republicans he would campaign for them if they backed the bill. Trump didn’t indicate what he would do to those who vote against the bill, but during that meeting, he singled out Rep. Mark Meadows, R-N.C., an outspoken critic of the bill.

Collins said Trump asked Meadows to stand up, called him a great guy and said he is counting on Meadows to get this over the line.

Another person at the event said Trump told Meadows, “I’m gonna come after you so hard.” Trump delivered that line with a smile, but it was also lined with a touch of seriousness, said the person, who spoke on condition of anonymity to describe a private meeting.

The Republican legislation would halt Obama’s tax penalties against people who don’t buy coverage and shrink the federal-state Medicaid program for low earners, which the statute has expanded.

It would provide tax credits for medical bills, though generally skimpier than the aid Obama’s statute provides. It also would allow insurers to charge older Americans more and repeal tax boosts the law imposes on high-income people and health industry companies.

The House Rules committee, usually tightly controlled by GOP leadership, was meeting today to set the terms of debate.

The panel was expected to let the chamber vote on revisions that top Republicans concocted to win votes. These include adding federal aid for older people and protecting upstate New York counties — but not Democratic-run New York City — from repaying the state billions of dollars for Medicaid costs.

Eager to showcase their support for Obama’s law, House Democrats invited former Vice President Joe Biden to speak today on the Capitol’s steps. Democrats champion the statute for its expansion of health care coverage to 20 million more people and requiring insurers to cover the very ill, families’ grown children to age 26 and specified services like mental health care.

While victory remained uncertain in the House, both sides were looking ahead to what could be an even tougher Senate fight.

Republicans control that chamber 52-48 and six GOP senators have already said they oppose the legislation.